Patterning Device Cooling via Differential Gas Flow
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Solution Overview
Problem
Conventional lithographic apparatuses face challenges in achieving precise alignment and overlay accuracy due to thermal variations in patterning devices and support structures, which current correction systems inadequately address, especially as device dimensions scale down.
Innovation Solution
A patterning apparatus with a conditioning system featuring separate gas outlets for the patterning device and support structure, allowing independent control of temperature and gas flow rate to manage thermal variations, with the support structure's gas outlet set to a higher temperature than the patterning device's.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional correction systems (alignment systems, magnification correction, feed forward systems) are used to address thermal expansion, then some level of correction is achieved, but alignment and overlay accuracy is insufficient for scaled down devices
Solution Approach 1:
The patent applies preliminary action by actively cooling the patterning device support structure before and during radiation exposure to prevent thermal expansion from occurring in the first place. Temperature control apparatus maintains the support structure at a predetermined temperature, and gas flows are provided in advance to counteract the thermal effects of the radiation beam before they can cause alignment errors.
Solution Approach 2:
The patent changes the temperature parameter of the support structure by providing controlled gas flows at different temperatures. The system varies gas flow rates and temperatures dynamically to compensate for thermal expansion, using different cooling strategies for different regions of the support structure based on their thermal sensitivity and radiation exposure.
2Productivity
If radiation beam is used for patterning, then pattern transfer is achieved, but thermal effects cause expansion and alignment errors
Solution Approach 1:
The patent converts the harmful thermal effects of radiation absorption into a beneficial controlled process. By providing targeted gas flows to specific regions of the support structure, the system uses the thermal energy from radiation to drive convection currents that enhance heat removal. The gas flows are strategically directed to maximize cooling efficiency in high-radiation areas while minimizing interference with the patterning process.
3Stability of the object's composition
If gas flow is provided to cool the patterning device, then thermal stability is improved, but complex temperature control is needed for different regions
Solution Approach 1:
The patent segments the support structure into multiple regions with different thermal characteristics and provides dedicated gas flows for each region. The support structure is divided into first, second, and third regions, each receiving gas flows optimized for its specific thermal load and geometric properties. This segmentation allows independent control of temperature in each zone, achieving uniform thermal stability across the entire structure.
Solution Approach 2:
The patent applies local quality by providing different gas flow rates, temperatures, and directions to different regions of the support structure based on their specific thermal requirements. High-radiation areas receive stronger cooling flows, while low-radiation areas receive gentler flows. The gas flow parameters are locally optimized to match the thermal conductivity, mass, and radiation exposure of each specific region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances thermal stability and reduces alignment and overlay errors by uniformly controlling temperature across the patterning device and support structure, improving precision in pattern formation.
Implementation Method 1
a first gas outlet providing a gas flow over a surface of the patterning device
Implementation Method 2
the temperature of the gas exiting the second gas outlet is at a higher temperature than the gas exiting the first gas outlet
Data Source
AI summary
An apparatus and method for controlling temperature of a patterning device in a lithographic apparatus, by flowing gas across the patterning device. A patterning apparatus includes: a patterning device support structure configured to support a patterning device; a patterning device conditioning system including a first gas outlet configured to provide a gas flow over a surface of the patterning device and a second gas outlet configured to provide a gas flow over a part of a surface of the patterning device support structure not supporting the patterning device; and a control system configured to separately control the temperature of the gas exiting the first and second gas outlets such that the gas exiting the second gas outlet is at a higher temperature than the gas exiting the first gas outlet and/or to separately control the temperature and gas flow rate of the gas exiting the first and second gas outlets.